Microfluidic devices are increasingly being used in a variety of settings to perform various chemical and physical processes. Applications include, but are not limited to, biochemical testing instrumentation, industrial process control equipment, and ink jet technology. Biochemical testing for research and diagnostic applications often involves performing assays including a large number of analytes in conjunction with one or a few biological samples. In some cases, it may be desirable to analyze one or a few biological samples using a single test device with a large number of analytes while requiring a small amount of sample. To this end, biochemical testing is increasingly being performed using microfluidic devices that define a network of microfluidic flow structures, including, for example, chambers, wells, channels, reservoirs, and other microfluidic flow structures.
It may be desirable to distribute one or more biological samples and/or analytes within a substrate defining a network of microfluidic flow structures and to control the flow of those distributed fluids via flow control mechanisms. Further, it may be desirable to isolate (e.g., seal from gases and/or liquids) various portions of the microfluidic flow structures while performing a chemical reaction, such as, for example, a polymerase chain reaction (PCR) and/or while otherwise processing the sample, including, for example, sample preparation. Isolation of biological sample and/or chemical assays within a substrate or other biological testing device may be desirable to avoid cross-contamination of various substances within a biological testing device, such as, for example, a microfluidic substrate which defines a network of sample distribution channels and chambers. Various techniques have been used to achieve isolation, such as, for example, mechanically deforming a laminate layer of the substrate.
It may be desirable, however, to provide a mechanism to achieve flow control and/or isolation of chambers, channels and/or other microfluidic flow structures of microfluidic device that does not rely on mechanical and/or external actuation devices. It also may be desirable to provide a mechanism to achieve flow control and/or isolation that reduces wear. It may further be desirable to provide a mechanism for achieving isolation and/or flow control (e.g., valving) that provides control over the rate at which the isolation and/or valving occurs, and/or that permits the passage of some gases and/or liquids while preventing the passage of other gases and/or liquids, and/or that permits diffusion of some gases and/or liquids. Additionally, it may be desirable to provide a relatively inexpensive mechanism to achieve isolation and/or flow control that is relatively easy to manufacture and use.